Process of making activated, recurable, durable-press fabrics and the product

ABSTRACT

Durable-press fabrics which are very active to recuring reactions are produced by depositing activating catalysts in durable-press fabrics which have carboxylic acid groups covalently bonded to the cellulose of the fibers. Sharp, permanent creases can be formed in these activated fabrics without severe strength losses by pressing and heating them under mild conditions of time and temperature.

United States Patent [191 Franklin et al.

[ 1 Feb. 25, 1975 [54] PROCESS OF MAKING ACTIVATED,

RECURABLE, DURABLE-PRESS FABRICS I AND THE PRODUCT Inventors: William E. Franklin; Stanley P.

Rowland; John P. Madacsi, all of New Orleans, La.

Assignee: The United States of America as represented by the Secretary of Agriculture, Washington, Filed: Sept. 29, 1972 9 Appl. No.: 293,744

US. Cl 8/182, 8/185, 8/120 Int. Cl D06m 3/00 Field of Search 8/116 R, 116.4, 181, 182,

Primary Examiner-Stephen J. Lechert, Jr.

[57] ABSTRACT Durable-press fabrics which are very active to recuring reactions are produced by depositing activating catalysts in durable-press fabrics which have carboxylic acid groups covalently bonded to the cellulose of the fibers. Sharp, permanent creases can be formed in 9 these activated fabrics without severe strength losses by pressing and heating them under mild conditions of time and temperature.

4 Claims, No Drawings PROCESS OF MAKING ACTIVATED, RECURABLE, DURABLE-PRESS FABRICS AND THE PRODUCT A non-exclusive, irrevocable, royalty-free license in the invention herein described, throughout the world for all purposes of the United States Government, with power to grant sublicenses for such purposes, is hereby granted to the Government of the United States of America.

FIELD OF THE INVENTION This invention relates to the improvement of cellulosic durable-press fabrics. Specifically, this invention relates to the modification of durable press cellulosic fabrics in such a way that they are capable of accepting sharp, permanent creases when pressed and heated under mild conditions of time and temperature. More specifically, this invention relates to combinations of catalysts and fabrics in which the fabrics are capable of undergoing rapid recuring reactions at moderate temperatures. More specifically, this invention relates to combinations of catalysts and fabrics in which the fabrics are capable of undergoing rapid recuring reactions at moderate temperatures. This invention constitutes a process whereby improved durable-press fabrics or articles manufactured therefrom may be pressed or subjected to other heat treatments to form sharp, permanent creases or other permanent configurations in the treated textiles or textile articles.

BACKGROUND AND PRIOR ART It is well known to those versed in the art of textile treatment that wrinkle-resistance and smooth-drying properties are imparted to cellulosic or cellulosic blended fabrics by chemical treatments which establish crosslinks between the molecules of the cellulose fibers, The crosslinks fix the fibers, and therefore the fabric, in the configuration present at the time the crosslinks are established. The covalent nature of the crosslinks makes it impossible to change the configuration of the treated fabric without a chemical reaction which involves breaking the crosslinks and reforming them in new positions to bind the fibers, and therefore the fabric, in the new configuration, Such reactions are known as recuring reactions.

In examining the prior art for solutions to this problem of unalterability of crosslinked cellulosic textile products, we find several approaches to solutions to this problem. One approach is through the use of thermally reversible crosslinks, that is, crosslinks which break and reform in new positions when heated. Another approach to alterable, crosslinked cellulosic fabrics is through internally catalyzed fabrics, that is, fabrics containing catalytic groups covalently bonded to the cellulose of the fibers, along with conventional crosslinks. One promising type of internally catalyzed, crosslinked cellulosic fabric is produced by the use of polycarboxylic acids as coreactant curing catalysts with methylol crosslinking reagents in cotton finishing treatments, as described, for an example in US. Pat. application Ser. No. 248,200, filed Apr. 25, 1972. In this process, the polycarboxylic acid serves as the catalyst which facilitates the formation of crosslinks in the cellulose matrix by the methylol reagent and at the same time becomes covalently bonded to the cellulose by the formation of ester bonds between the cellulose hy- 'are capable of catalyzing recuring reactions in the crosslink cellulosic fabric. In these reactions, the carboxylic acid groups catalyze the breaking of the methylol crosslinks and the reformation of these crosslinks in new positions which hold the fibers, and therefore the fabric, in the configuration present during the recuring operation.

These fabrics, prepared by treating cellulosic fabrics with a combination of a methylol crosslinking reagent and a polycarboxylic acid, have good durable press resilience properties and a sufficient degree of recurability to accept sharp, permanent creases when subjected to a high temperature recuring operation. However, the high temperature recuring operation with these fabrics is not entirely satisfactory, since the time required to form sharp, durable creases in these fabrics'is on the order of three to four minutes. This is an inconveniently long time for use with conventional pressing equipment (hand irons or hot head presses) and makes it impractical to use these fabrics in conventional garment manufacturing, home sewing, or other garment alteration applications.

A similar type of internally catalyzed, durable-press fabric is prepared by the use of relatively large amounts of hydroxy acids as coreactant catalysts with methylol crosslinking reagents in treating cellulosic fabrics as described by Franklin, Madacsi, and Rowland in Abstracts of Papers presented at the 163 rd National ACS Meeting, Apr. 9-14, 1972, Abstract No. 3l of the Cellulose, Wood and Fiber Division. These fabrics have the same advantages and disadvantages as fabrics prepared using the polycarboxylic acids as described above.

It is also found in the prior art that crosslinked cellulosic fabrics may be given new, durable configurations when a catalyst is applied to the cured fabric and the the fabric but may be washed out of the fabric with wadroxyl groups and a portion of the carboxylic acid ter. The reagents employed in this type of recuring process are usually strong catalysts, and consequently have adverse effects on the strength of the fabric and the durable-press properties of the treated areas of the fabric.

The use of added catalysts with conventional durable-press cellulosic fabrics having high levels of resilience and smooth-drying properties is particularly unsuitable because large amounts of very strong catalysts must be used if it is desired to form sharp, durable creases in reasonable lengths of time at moderate temperatures. Suchcatalysts cause serious strength losses when used in amounts or/and at temperatures sufficient to form creases of acceptable sharpness and durability in conventional durable-press fabrics.

OBJECTS OF THE INVENTION A primary object of the present invention is to provide a process for the rapid formation of permanent creases or other configurations in wrinkle-resistant, smooth-drying cellulosic fabrics, while avoiding the problems of long heating periods or substantial losses of strength which are characteristic of the processes in the prior art as described above.

Another object of the present invention is to provide wrinkle-resistant, smooth-drying cellulosic fabrics which may be formed into permanent creases or other configurations by a rapid heat treatment.

Yet another object of the present invention is to provide cellulosic fabrics having the properties commonly referred to as durable press, but also having the ability to be formed permanently into desirable shapes, such as sharp creases or flat seams, by conventional techniques such as hand ironing or pressing with commonly available commercial equipment such as hot-head presses.

Yet another object of the present invention is to provide fabrics suitable for home sewing of durable press garments or fabrics suitable for manufacture of durable-press garments which may be altered in the home or in the retail outlet.

These and other objects of the present invention will become more clearly apparent from the following description.

SUMMARY OF THE lNVENTlON We have discovered that wrinkle-resistant cellulosic fabrics containing carboxylic acid groups covalently bonded to the cellulose of the fibers may be impregnated with activating catalysts to accelerate and facilitate the formation of permanent creases or other configurations by heat treatments. The addition of activating catalysts enhances the recurability of these fabrics and thereby reduces the time and temperature of the heat treatment required to form sharp, permanent creases in the activated fabric such that conventional pressing or ironing techniques may be used in the heat treatment. A particularly attractive feature of this discovery is the fact that the activating catalysts do not cause severe strength losses in the fabric during the heat treatment, since the activating catalysts used in this invention are not the very strong mixed acid catalysts which are normally required to form permanent creases in conventional durable-press fabrics. In addition, the process is applicable to all-cellulosic fabrics as well as blended fabrics and does not rely on polyester or other synthetic thermoplastic fibers blended with the cellulosic fibers to form and hold the creases.

In the process of this invention. the activating catalyst is deposited in fabrics which contain carboxylic acid groups covalently bonded to the cellulose of the fibers. Thus, an active catalyst combination is formed within the fabric at the sites of the carboxylic acid groups, and not throughout the whole fabric. Since the carboxylic acid groups are capable of catalyzing recuring reactions, although slowly, the metal salt catalysts may be termed activating catalysts, that is, catalysts which activate the carboxylic acid groups in their ability to catalyze recuring reactions. Thus the activating catalyst may be said to be synergistic with the carboxyl groups in its catalytic activity. The formation of the active catalyst combination at the sites of the recuring reaction greatly accelerates the recuring reaction, but the fabric does not contain a large excess of the strong recuring catalyst. This combination of the active catalyst system at the sites of the recuring reaction and the mild catalyst distributed throughout the remainder of the fabric results in a unique combination of a very rapid recuring reaction without the usual accompanying large strength losses. This combination of properties would not be predicted on the basis ofthe prior art.

It is possible that the carboxylic acid groups may be attached to the cellulose at positions close to the crosslinking residues and therefore at positions primarily associated with resilience properties but not with strength properties. Thus, there is an unexpected synergism between the covalently bonded catalytic groups and the activating catalysts such that only the catalysis of recuring reactions is accentuated without the undesirable degradation caused by the strong catalysts which are conventionally added to the fabric to promote recuring reactions.

DESCRIPTION OF. THE INVENTION The fabrics used in this invention are cellulosic or cellulosic blended fabrics which have carboxylic acid groups covalently bonded to the cellulose of the fabric and also have wrinkle-resistant properties resulting from crosslinks introduced by reactions of these fabrics with methylol-type crosslinking reagents. The fabrics used in this invention may be in the form of piecegoods or in the form of garments or other articles manufactured from these fabrics. The preferred fabrics for use in this invention are cotton fabrics which have been treated with combinations of a methylol crosslinking reagent and a polycarboxylic acid or cotton fabrics which have been treated with a combination of a methylol crosslinking reagent and a hydroxy acid. Other cellulosic fabrics which have been manufactured by the reactions of methylol crosslinking reagents with carboxyl containing fabrics, such as carboxyethylated cotton, carboxymethylated cotton, or various oxidized cotton fabrics may also serve as the carboxylic acid containing fabrics of this invention, butthese are not the preferred fabrics because of the difficulty or inconvenience in manufacturing such fabrics. Of course, fabrics made of a blend of any of these cellulosic fibers with synthetic fibers, such as polyester fibers or polyamide fibers, may also be used in this invention. The

fabrics used in this invention must have a fairly high level of resilience or wrinkle-recovery if the creases formed by the process of this invention are to be sharp and permanent; and the resilience must be a result of chemical crosslinks formed by methylol reagents in order for the combination of carboxylic acid groups and activating catalysts to be effective in rearranging these crosslinks to form sharp, permanent creases or other configurations.

The preferred fabrics of this invention are those in which the crosslinks have been formed by the reaction of the carboxyl containing cellulosic fabric with dimethylolihydroxyethyleneurea (DMDHEU), although carboxylic acid containing fabrics crosslinked with other reagents, such as methylol melamine reagents, urea-formaldehyde reagents, methylol uron, methyloltriazines, and methylolcarbamates are also suitable for use in this invention. The fabrics of this invention may also contain other useful additives, such as polymeric softening agents, which do not interfere with the catalytic action of the activating catalyst and carboxyl groups during the heat treatment. To recapitulate the most suitable fabrics for use in this invention are cellulosic fabrics which have been treated with a combination of DMDHEU and either a polycarboxylic acid or a hydroxy acid.

It is preferable that the fabrics of this invention be washed after the original treatment to remove unreacted crosslinking reagents and acids which might combine with the activating catalyst causing detrimental effects on the fabric during the heat treatment. The crosslinked fabric may be stored for any period of time before the activating catalyst is applied.

Substantially any catalyst normally used for the curing of crosslinking reactions of methylol reagents in cellulose may be used as the activating catalyst in the process of this invention. These catalysts are generally metal salts which behave as latent acids at curing temperatures. Our preferred activating catalysts are magnesium chloride hexahydrate and zinc nitrate hexahydrate, although other metal salt catalysts which may be employed include aluminum chloride, zinc chloride, magnesium dihydrogen phosphate, calcium chloride, ammonium chloride, and aluminum chlorohydroxide.

The activating catalyst may be applied to the fabric by any convenient method, provided that the catalyst is thoroughly distributed throughout the cellulosic fibers. This is best accomplished by applying a solution of the catalyst in water to the fabric. Our preferred method is to impregnate the fabric by immersing it in a solution of the catalyst in water. The wet fabric may be passed through rollers to squeeze out the excess solution and distribute the catalyst throughout the fibers. The fabric may be dried in a separate step before the heat treatment, but this is not necessary, as the drying and the heat treatment may be combined into one operation. The dried fabric containing the activating catalyst may be stored for any period of time between the impregnation and drying and the heating treatment. It is of course possible to use other methods of applying the catalyst, such as spraying a solution of the catalyst onto the area of the fabric to be subjected to the heat treatment.

If the carboxyl groups of the fabric have been neutralized and are in a salt form, it is necessary that they be converted to the acid form before or during the impregnation of the fabric with the activating catalyst. This may be done conveniently by rinsing the fabric with a weakly acidic solution, such as a l to 5% by weight solution of acetic acid in water. The weak acid, such as acetic acid, may be combined with the activating catalyst during the impregnation, but this is not preferable, since in this case a large excess of the solution must be used in the impregnation. Obviously, only a volatile acid which is removed during the drying step can be used in this application.

The amount of catalyst applied to the fabric can vary over a wide range, but for best results between 0.3% and 4% by weight of the catalyst is applied. The amount of catalyst depends on the activity of the catalyst and the original treatment of the fabric. Larger amounts of catalyst are used with the less active catalysts and with fabrics containing smaller amounts of carboxylic acid groups. The concentration of the catalyst in the solution is adjusted to give the desired amount of catalyst on the fabric according to the construction of the fabric and to the method of application.

The impregnated fabric is subjected to a heat treatment during which it is constrained in the new desired configuration. The textile may be constrained by folding it in the desired configuration and applying pressure, as from a hand iron or other heated object. This may also be accomplished with a steam or electrically heated hot-head press. Additional pressure may be applied in order to produce sharp creases. The textile may be wet or dried when it is constrained and heated, but

peratures of the heat treatment may vary between 100 )C. and 220C., and the time of the treatment may vary from a few seconds to five minutes. In the preferred process, the impregnated textile is folded at the position of the desired new crease, placed on a preheated surface, and covered with a heated hand iron. 1n the preferred process, the temperature in the textile is maintained at 160 C., and the textile is held at this temperature for about 15 seconds.

Fabrics prepared andgiven heat treatments according to the process of this invention permanently retain the new creases or other configurations imparted by the heat treatments. Thus, textiles prepared by the preferred process and given creases according to the pre ferred heat treatments retain creases rated at 4.0 or better according to the AATCC crease appearance tests after five machine washes and tumble drying cycles.

The following list of examples is presented to illustrate this invention and is not meant to limit its scope in any manner whatever.

EXAMPLE 1 Cotton twill fabric (7.6 ozlyd was impregnated to wet pickup with a solution containing 12% by weight of dimethyloldihydroxyethylene urea (DMDHEU), 6% by weight of cyclopentanetetracarboxylic acid (CPTA), 2% by weight of an emulsified polyethylene softener, and 0.1% by weight of a nonionic wetting agent. The fabric was dried for 8 minutes at 70 C., then cured for 8 minutes at C. After washing in water with a nonionic detergent, the fabric had an add-on of 9.1% and a conditioned wrinkle recovery angle (WRA) (determined by the procedure of ASTM Designation B 1295-67) of 306 (W+F) and a wet WRA of 276 (W+F). A portion of the fabric was analyzed for nitrogen by the Kjeldahl method and for formaldehyde by the chromotropic acid method. The fabric was found to contain 1.29% N and 1.43% formaldehyde. A portion of the fabric was analyzed for free carboxyl groups by a titration (as described by Reinhardt, Fenner, and Reid, in Textile Research Journal, Vol. 27, p. 873 (1957)). The fabric was found to contain 0.33 meq/g of carboxylic acid groups covalently bonded to the fabric. These analyses indicate that the textile contained crosslinks from the methylol reagent (DMDHEU) and partial ester and free carboxylic acid groups from the polycarboxylic acid (CPTA). This example illustrates the preparation of a carboxylic acid containing, wrinkle-resistant cotton fabric from a methylol crosslinking reagent and a polycarboxylic acid.

EXAMPLE 2 Cotton twill fabric was treated according to the process of Example 1 except that 6% by weight of hydroxyacetic acid was used in placeof the CPTA. The fabric had a conditioned WRA of 308 (W+F) and a wet WRA of 279 (W+F). This fabric was found by analyses to contain 121% N, 1.77% formaldehyde, and 0.32 meq/g of carboxylic acid groups covalently bonded to the fabric. This Example illustrates the preparation of a wrinkle-resistant cotton fabric containing covalently bonded carboxylic acid groups from a combination of a methylol crosslinking reagent and a hydroxy acid.

EXAMPLE 3 Cotton twill fabric treated according to the process of Example 1 was impregnated with a solution containing 0.3% by weight of zinc nitrate and dried. A portion five machine washings and tumble drying cycles. Afterthe last drying cycle, the crease remaining in the fabric sample was evaluated by the AATCC Test Method 88 C-l969 modified as described by Hobart in Textile Research Journal, Vol. 37, p. 380 (1967). The crease retained in this fabric after the laundering cycles was rated at 4.8 on the AATCC scale (running from -no crease to excellent). This example indicates that good, very durable creases are imparted to fabrics prepared according to Example 1 and treated according to this example by impregnation with an activating catalyst and a heat treatment. The conditions of this heat treatment may be easily obtained in the home with a hand iron or in commercial establishments with a conventional hot-head press.

EXAMPLE 4 Cotton twill fabric treated according to the process of Example 2 was impregnated with a solution containing 0.3% of zinc nitrate and dried. The dried fabric was subjected to a heat treatment as described in Example 3. After five laundering cycles, the fabric sample retained a crease with an AATCC crease rating of 4.7.

EXAMPLE 5 Cotton twill fabric prepared according to the process of Example I was treated according to the process of Example 3, except that the impregnation solution contained 3% of magnesium chloride hexahydrate in place of the zinc nitrate. After creasing by the heat treatment as described in Example 3 of seconds at 160C, and

flS

five laundering cycles. the fabric sample retained a crease with an AATCC crease rating of 5.0

EXAMPLE 6 Cotton twill fabric prepared according to the process of Example 2 was impregnated with a magnesium chloride solution and given a heat treatment according to the process of Example 5. After the five laundering cycles, this fabric sample retained a crease with an AATCC crease rating of 5.0

EXAMPLE 7 solution for 30 minutes, then dried. Samples of these impregnated fabrics were subjected to heat treatments as described in Example 3, except that various times and temperatures were used in the heat treatments. The time of heating, the temperature of the heat treatment, and the AATCC crease ratings of the creases remaining in each sample after five laundering cycles are given in Table I.

TABLE 1 Temperature (C) Time (sec) AATCC Crease Rating PCA Fabic HA Fabric l3O 15 2.7 3.l 145 15 4.0 4.l 160 l5 4.8 4.7 180 15 5.0 5.0 220 15 5.0 5.0 160 5.0 5.0 160 300 5.0 5.0

The results in Table l demonstrated the range of conditions of time and temperature for heat treatments according to this'invention.

Samples of each fabric treated according to the process of this Example and creased for 15 seconds at 160 C. were tested for breaking strength according to ASTM Designation B 1 682-64. The fabric samples were found to have retained (PCA Fabric) and 92% (HA Fabric) of their breaking strength after the heat treatments. This experiment demonstrates that very sharp, durable creases may be formed in fabrics treated according to this invention without causing serious strength losses.

Cotton twill fabric was treated according to the process of Example 1, except that 4% of magnesium chloride hexahydrate was used in place of the CPTA. This treatment produced a conventional durable press cotton fabric. Samples of this conventional durable press fabric were treated with zinc nitrate solution and given heat treatments according to the process of this Example. A heat treatment of 15 seconds at C. produced a crease with an AATCC crease rating of 0.7 after five launderings, and a heat treatment of 5 minutes at l 60 C. produced a crease with an AATCC crease rating of 2.3 after 5 launderings. These experiments demonstrate that the activating catalyst of this invention are effective for producing sharp, permanent creases during short heat treatments only in the fabrics of this invention, that is, cellulosic fabrics containing covalently bonded carboxyl groups and crosslinks derived from methylol reagents, and are not effective with conventional durable press fabrics.

EXAMPLE 8 Samples of cotton twill fabrics prepared according to the process of Example 1 (PCA Fabric) and samples of cotton twill fabrics prepared according to the process of Example 2 (HA Fabric) were impregnated with solutions containing 1% of various activating catalysts. The fabric samples were dried and subjected to heat treatments as described in Example 3. The activating catalyst and the AATCC ratings ofthe creases remaining in each fabric sample after five launderings are listed in Table ll.

We claim:

1. An improvement in the process for imparting durable press properties and permanent configurations to crosslinked cellulosic textiles obtained via impregnation of the cellulosic textile with a solution containing a polycarboxylic acid and a methylolated crosslinking reagent and subsequently drying, curing, and washing the cellulosic textile, which improvement consists of:

a. impregnating the cured and washed textile with a solution of a latent acid catalyst,

b. drying the impregnated textile from (a), and

c. thermally reforming, with restraint, the dried tex- 10 tile from (b) at a temperature of from about 100C to about 220C for a period of from about l seconds to about 300 seconds.

2. The product prepared by the process of claim 1.

3. An improvement in the process for imparting durable press properties and permanent configurations to crosslinked cellulosic textiles obtained via impregnation of the cellulosic textile with a solution containing a hydroxy acid and a methylolated crosslinking reagent and subsequently drying, curing, and washing the cellulosic textile, which improvement consists of:

a. impregnating the cured and washed textile with a solution of a latent acid catalyst,

b. drying the impregnated'textile from (a), and

c. thermally reforming, with restraint, the dried textile from b. at a temperature of from about 100C to about 220C for a period of from about 15 seconds to a b. t sec a 4. The product prepared by the process of claim 3. 

1. AN IMPROVEMENT IN THE PROCESS FOR IMPARTING DURABLE PRESS PROPERTIES AND PERMANENT CONFIGURATIONS TO CROSSLINKED CELLULOSIC TEXTILES OBTAINED VIA IMPREGNATION OF THE CELLULOSIC TEXTILE WITH A SOLUTION CONTAINING A POLYCARBOXYLIC ACID AND A METHYLOLATED CROSSLINKING REAGENT AND SUBSEQUENTLY DRYING, CURING, AND WASHING THE CELLULOSIC TEXTILE, WHICH IMPROVEMENT CONSISTS OF: A. IMPREGNATING THE CURED AND WASHED TEXTILE WITH A SOLUTION OF A LATENT ACID CATALYST, B. DRYING THE IMPREGNATED TEXTILE FROM (A), AND C. THERMALLY REFORMING, WITH RESTRAINT, THE DRIED TEXTILE FROM (B) AT A TEMPERATURE OF FROM ABOUT 100*C TO ABOUT 220*C FOR A PERIOD OF FROM ABOUT 15 SECONDS TO ABOUT 300 SECONDS.
 2. The product prepared by the process of claim
 1. 3. An improvement in the process for imparting durable press properties and permanent configurations to crosslinked cellulosic textiles obtained via impregnation of the cellulosic textile with a solution containing a hydroxy acid and a methylolated crosslinking reagent and subsequently drying, curing, and washing the cellulosic textile, which improvement consists of: a. impregnating the cured and washed textile with a solution of a latent acid catalyst, b. drying the impregnated textile from (a), and c. thermally reforming, with restraint, the dried textile from b. at a temperature of from about 100*C to about 220*C for a period of from about 15 seconds to about 300 seconds.
 4. The product prepared by the process of claim
 3. 